From Colorado's 2010 Amendment 62 Co-Sponsors
Rebutting Colorado's Legislative Council
2016 Update: A team of scientists from Northwestern University have photographic documentation of the "flash of light" that occurs at the moment of fertilization. See that here:
2018 Update: A University of Chicago study of biologists from over 1,000 institutions shows 95% of biologists know that human life begins at fertilization. (The other 5% are so obsessed with dismembering unborn children that they lie about the most fundamental science in the own field of expertise. And the left, that cries "consensus consensus", of course, couldn't care less about this consensus.)
Preliminary Comment on Beginning of Biological Development: The Colorado Legislative Council has persisted in claiming against all scientific and medical research and common usage of English grammar that the phrase "the beginning of biological development," is "a term which is not defined… and is not an accepted medical or scientific term." So prior to presenting our answers to the council's thirteen questions, we're summarizing references that address this matter first, for both sexual (fertilization) and asexual (twinning, cloning, etc.) human reproduction.
THE BEGINNING OF BIOLOGICAL DEVELOPMENT
1. SEXUAL HUMAN REPRODUCTION:
The following scientific references are provided by medical ethicist Dr. Prof. Dianne N. Irving of Georgetown University who herself writes herein, "Scientifically, the term 'embryo' as it refers to the sexually reproduced single-cell human embryo should apply from the biological beginning of that human organism, i.e., at the beginning of the process of fertilization or first contact of the sperm with the oocyte (as documented by Carnegie Stage 1)."
So, beginning this list of references with the widely influential Carnegie Stages of Early Human Embryonic Development:
Carnegie Stage 1 Definition: Embryonic life commences with fertilization, and hence the beginning of that process may be taken as the point de depart of stage 1. Despite the small size (ca. 0.1 mm) and weight (ca. 0.004 mg) of the organism at fertilization, the embryo is "schon ein individual-spezifischer Mensch" (Blechschmidt, 1972). ... Fertilization is the procession of events that begins when a spermatozoon makes contact with an oocyte or its investments and ends with the intermingling of maternal and paternal chromosomes at metaphase of the first mitotic division of the zygote (Brackett et al., 1972). Fertilization sensu stricto involves the union of developmentally competent gametes realized in an appropriate environment to result in the formation of a viable embryo (Tesarik, 1986) ... . Fertilization requires probably slightly longer than 24 hours in primates (Brackett et al., 1972). In the case of human oocytes fertilized in vitro, pronuclei were formed within 11 hours of insemination (Edwards, 1972). ... Fertilization, which takes place normally in the ampulla of the uterine tube, includes (a) contact of spermatozoa with the zona pellucida of an oocyte, penetration of one or more spermatozoa through the zona pellucida and the ooplasm, swelling of the spermatozoal head and extrusion of the second polar body, (b) the formation of the male and female pronuclei, and (c) the beginning of the first mitotic division, or cleavage, of the zygote. ... The three phases (a, b, and c) referred to above will be included here under stage 1, the characteristic feature of which is unicellularity. ... [see at cargnegiescience.edu from the Carnegie Stages of Early Human Embryonic Development, Stage 1.] (emphases added)
Human development is a continuous process that begins when an oocyte (ovum) from a female is fertilized by a sperm (or spermatozoon) from a male. (p. 2); ibid.: ... but the embryo begins to develop as soon as the oocyte is fertilized. (p. 2); ibid.: [Single-cell human embryo]: this cell results from the union of an oocyte and a sperm ... is the beginning of a new human being (i.e., an embryo). (p. 2); ibid.: Human development begins at fertilization, the process during which a male gamete or sperm ... unites with a female gamete or oocyte ... to form a single cell [embryo] . This highly specialized, totipotent cell marks the beginning of each of us as a unique individual. (p. 18) ... The usual site of fertilization is the ampulla of the uterine tube [fallopian tube], its longest and widest part. If the oocyte is not fertilized here, it slowly passes along the tube to the uterus, where it degenerates and is reabsorbed. Although fertilization may occur in other parts of the tube, it does not occur in the uterus. ... The embryo's chromosomes sex is determined at fertilization by the kind of sperm (X or Y) that fertilizes the ovum; hence it is the father rather than the mother whose gamete determines the sex of the embryo. [Keith Moore and T.V.N. Persaud, The Developing Human: Clinically Oriented Embryology (6th ed. only) (Philadelphia: W.B. Saunders Company, 1998), p. 37] (emphases added)
Human pregnancy begins with the fusion of an egg and a sperm. (p. 3); ... finally, the fertilized egg, now properly called an embryo, must make its way into the uterus (p. 3); ... The sex of the future embryo is determined by the chromosomal complement of the spermatozoon ... Through the mingling of maternal and paternal chromosomes, the [embryo] is a genetically unique product of chromosomal reassortment ... [Bruce M. Carlson, Human Embryology and Developmental Biology (St. Louis, MO: Mosby, 1994), p. 31; ibid, Carlson 1999, pp., 2, 23, 27, 32] (emphasis added)
In this text, we begin our description of the developing human with the formation and differentiation of the male and female sex cells or gametes, which will unite at fertilization to initiate the embryonic development of a new individual. ... Fertilization takes place in the oviduct [not the uterus]... resulting in the formation of an [embryo] containing a single diploid nucleus. Embryonic development is considered to begin at this point. (p. 1); ... [William J. Larsen, Human Embryology (New York: Churchill Livingstone, 1997), p. 17] (emphases added)
Fertilization is an important landmark because, under ordinary circumstances, a new, genetically distinct human organism is thereby formed. (p. 5); ibid.: Fertilization is the procession of events that begins when a spermatozoon makes contact with a secondary oocyte or its investments ... (p. 19); ibid.: "The ill-defined and inaccurate term pre-embryo, which includes the embryonic disc, is said either to end with the appearance of the primitive streak or ... to include neurulation. The term is not used in this book. [Ronan O'Rahilly and Fabiola Muller, Human Embryology & Teratology (New York: Wiley-Liss, 1994), p. 55] (emphases added)